A grain quality level discrimination device emitting light to grains, receiving a reflected and/or transmitted light from the grains, and discriminating the quality level of the grains on the basis of a received signal is well known in the art (for example, see Patent Literature 1).
The grain quality level discrimination device of the Patent Literature 1 includes a conveying unit for conveying grains, two optical detection units arranged in the conveying direction of the conveying unit, and a quality level discrimination unit.
The first optical detection unit of the grain quality level discrimination device is provided with a red light emitting diode lamp that emits red light obliquely from above to the grain, a green light emitting diode lamp that emits green light, and a blue light emitting diode lamp that emits blue light from below to the grain. The first optical detection unit is also provided with a RGB image sensor for receiving reflected or transmitted light from the upper and side surfaces of the grain illuminated by the lamps.
The second optical detection unit of the grain quality level discrimination device is also provided with a green light emitting diode lamp that emits green light obliquely from above to the grain, a blue light emitting diode lamp that emits blue light from above to the grain, and a red light emitting diode lamp that emits red light obliquely from below to the grain. The second optical detection unit is also provided with, a RGB image sensor that receives reflected or transmitted light emitted from the respective lamps from the lower surface of the grain.
The grain quality level discrimination device identifies the upper surface (planar) shape of the grain on the basis of the blue light transmitted through the grain and received by the RGB image sensor. The grain quality level discrimination device further acquires “upper-side information” of the grain such as color information, stain information, transparency information, and the like on the basis of the red, green, and blue lights from the upper surface of the grain received by the RGB image sensor.
Also, in the quality level discrimination unit, the shape of the side surface of the grain is identified on the basis of the transmitted light of any color from the side surface of the grain and received by the RGB image sensor of the first optical detection unit, so that “grain thickness information” of the grain is obtained on the basis of the shape of the side surface of the grain.
Further, the quality level discrimination unit identifies the lower surface (planar) shape of the grain on the basis of the transmitted blue light from the lower surface of the grain, the transmitted light being received by the RGB image sensor of the second optical detection unit, so as to obtain “lower-side information” of the grain such as stain information, crack information, and the like on the basis of the red, green, and blue lights from the lower surface of the grain that has been received by the RGB image sensor.
According to the grain quality level discrimination device described in Patent Literature 1, the quality of the grain conveyed by the conveying unit can be discriminated accurately by the “upper-side information” and the “grain thickness information” obtained on the basis of the reflected and/or transmitted light from the upper and side surfaces of the grain and received by the RGB image sensor of the first optical detection unit, and the “lower-side information” of the grain obtained on the basis of the reflected and/or transmitted light from the lower surface of the grain and received by the RGB image sensor of the second optical detection unit.
However, since the grain quality level discrimination device includes two identical optical detection units having the same scanning speed, the device involves the problem that it needs a large arrangement space and the size of the device becomes large, causing cost increases.
The grain quality level discrimination device includes a pair of the optical detection units disposed along the grain conveying direction, so that it is not possible to receive the reflected or transmitted light from the upper and side surfaces of the grain and that from the lower surface of the grain lower surface at the same time. As a result, if there is a small difference in the conveying speeds upon passing through the optical detection units, then the amount (number of times) of the light reception signal from the upper and lower surfaces of one grain can be differed (i.e. the problem of instability of the moving speed exists). Also, if the attitudes of the grain at the time of passing the two optical detection units are not completely identical with each other, then the identified planar shape differs between the upper and lower surfaces of the one grain (i.e. the problem of variation of the attitude of the grain in the course of the conveyance exists). Upon taking these problems into account, it is clear that there is room for improving the accuracy of discrimination of the quality level of the grain.
In order to solve the above mentioned problems, it might be better to receive the reflected and/or transmitted light from the upper, lower, and side surfaces of the grain simultaneously by one single optical detection unit of the grain quality level discrimination device. However, with regard to the side to be irradiated with the blue light required for identifying the planar shape of the grain, traditionally, the light source that emits the blue light interferes with the reception of the reflected and/or transmitted light from the grain.
Although the grain quality level determining devices disclosed in Patent Literatures 2 and 3 are of the same or similar structure as those of Patent Literature 1, a reference plate provided at any recess of a rotating disk is referred therein.
The grain quality level discriminating devices of Patent Literatures 2 and 3 is adapted to correct by using the reference plate, the variation of the characteristics of the optical elements such as the light sources and the photosensors of the optical detection unit due to the influence of the variation of the temperature inside of the main body and the like. However, the reference plate provided at the recess of the rotating disk of the grain conveying unit is apt to be scratched and stained by the grain and the like supplied thereto and brought into contact therewith, so that it leads to the degradation in the accuracy of the quality level discrimination of of the grains.
Also, in accordance with the above-described grain quality level discrimination device, the reference plate is provided at the recess of the rotating disk of the grain conveying unit, so that, when the reference plate is damaged, any broken piece of it may be mixed into the grains supplied onto the rotating disk.
Further, the grain quality level discrimination device described in Patent Literature 4 is well known. However, the grain quality level discrimination device described in Patent Literature 4 adopts a scheme of correction that uses reflected light from a reference plate of the rectangular parallelepiped shape mounted in a planar fashion to a recess in a rotating disk. In this connection, the amount of light received from the side surface of the reference plate is very small and it is not possible to obtain a correction coefficient with regard to the side surface side information. As a result, there is a problem that the correction had not been made successfully.